1. Field of the Invention
The present invention relates to an image processor for encoding and/or decoding image signals having different frequency bands and an apparatus for recording and reproducing encoded image signals having different frequency bands.
2. Description of the Related Art
Recently, long hour recording and reproducing have been made possible by efficiently encoding an image signal to record compressed image data. Various kinds of highly efficient coding methods have been proposed. In particular, the DCT coding method that divides an image into several blocks, transforms each block by the discrete cosine transform (DOT), and quantizes and encodes the DCT coefficients is widely used.
Also, there have been proposed methods that decompose an image signal into components in several frequency bands and encode each component by a method suitable for each hand. Among these methods are the subband coding method and the wavelet-transform coding method, each recursively iterating a band decomposition that decomposes an image signal into a high band component and a low band component by filters, so that each decomposed component is encoded by a method suitable for that component through subsampling.
As recording and reproducing apparatus for image signals, VTRs and laser disk players are commercialized for consumers to record and reproduce standard image signals such as a transient image signal in the NTSC system, the PAL system and the like. However, digitizing and high image quality have been demanded by industrial areas, and products aimed at these needs are also commercialized. For example, apparatus for recording and reproducing a transient analog image signal in the NTSC system by temporally separating the luminance signal and color signals to prevent their mutual interference and apparatus for recording still and transient images in a high definition digital system are commercialized. Further, apparatus for recording and reproducing high definition images is in the process of marketing for consumers.
Also, digitizing and high image quality have been developed in transmitting and reproducing apparatus as in recording and reproducing apparatus.
However, apparatus for recording and reproducing a high definition image signal tends to be large scale and expensive compared with apparatus for recording and reproducing standard image signals, because the former has to process a high resolution image signal. Also, separate pieces of apparatus are needed in order to record and reproduce both a high definition image signal and a standard image signal. Transmitting and reproducing apparatus and disk apparatus have also the same problems.